Slice chicken breasts in half lengthwise if not using cutlets.
In a large bowl, mix olive oil, lemon zest and juice, chicken stock, garlic, cumin, smoked paprika, coriander, cinnamon, salt, and pepper.
Add chicken and coat well. Cover and refrigerate for at least 2 hours or up to 24 hours.
In a small bowl, combine all garlic sauce ingredients until smooth. Adjust milk for desired consistency. Refrigerate for at least 1 hour.
Remove chicken from marinade, discard marinade, and pat chicken dry.
Grill or Skillet: Cook over medium-high heat for 3–4 minutes per side.
Air Fryer: Cook at 370°F for 5 minutes, flip, then cook another 4–5 minutes.
Rest chicken for 5 minutes before slicing.
Serve chicken shawarma with garlic sauce in pita or bowls with desired toppings.